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Chapter III
The tissues and organs of immune system
Immune system
immune organs or tissues
bone marrow
lymph nodes
Immune cells :
lymphocytes : T cells , B cells and NK cells
phagocytes: Dendritic cells ,macrophage ,PMN
immune molecules :
complement (补体)
adhesive molecules
Immune organs
Central immune organs or primary lymphoid organs
The site that lymphocytes generate and mature into
functional cells
Bone marrow or Bursa, and Thymus
, Thymus , Peripheral immune organs or secondary
lymphoid organs and tissues
The sites that T and B lymphocytes reside in and
respond to antigens
spleen , lymph nodes , mucosal immune system
Section I Central immune tissues and organs
I. Bone marrow
1.The bone marrow is the site of generation of all
circulating blood cells in the adult, including
immature lymphocytes
2. The bone marrow is the site of B cell maturation
3. Bone marrow is the sites that secondary
humoral immunity carries through
II. Thymus
1. The structure of thymus
outer cortex : immature T cells ( thymus cells)
inter cortex : thymus epithelial cell, macrophage , DC
Mature T cells + thymus epithelial cell, macrophage , DC
The structure of thymus
2. The function of thymus
The thymus is the site of T cell maturation
Secrete cytokine and thymulin-like molecules
To promote the proliferation , differentiation of
thymus cells
Barrier function:blood-thymus barrier
Development of T cell in thymus
Section II
Peripheral Immune tissues and organs
The immune organs /tissues or secondary
lymphoid organs/tissues are sites that T and B
lymphocytes reside in and respond to antigens
lymphoid nodes
mucosal immune system
(mucosal-associated lymphoid tissues, MALT)
I. Spleen
1. The Structure of spleen
white pulp
Central arteriole
periarteriolar lymphoid sheaths (PALS)
T–cell area : around the central arteriole
contain T cells , dendritic and macrophage
B -cell area: lymphoid follicles
contain B cells and macrophage and dendritic cells
primary lymphoid follicle
secondary lymphoid follicle
Red pulp:
cellular cords : B cells , plasma cells and macrophage ,DC
venous: blood
B ells
T cells
2. Function of spleen
The site of T and B cells residence
B cells : thymus-independent area
T cells : Thymus –dependent area
Site of immune response to antigens
Synthesize some bioactive substance
component of complete
Filtering blood
II. Lymphoid nodes
Cortex :
Structure of Lymphoid
node( p38)
Outer cortex: thymus-independent area : B cell-rich area
lymphoid follicle/lymphoid nodule :
primary lymphoid follicle : without germinal center
mature and naïve B cells
secondary lymphoid follicle : with germinal center
activated B cells and memory B cells and macrophage
Paracortex : T cell-rich area+ dendritic cells
Medulla :
medulla cords: macrophage and plasma cells
medulla sinus
2. Function of lymphoid node
The site of T and B cells residence
B cells : thymus-independent area
T cells : Thymus –dependent area
Site of immune response to antigens
Part of Recirculation of lymphocytes
Filtering blood
III. Mucosal immune system
Mucosal immune system, also named as
mucosa-associated lymphoid tissue, MALT)
is in the epithelia , lamina propria and
submucosal area of gastrointestinal,
respiratory and genitourinary tract
(I)The constitution of MALT
Gut-associated lymphoid tissue, GALT
Nasal-associated lymphoid tissue, NALT
Bronchial-associated lymphoid tissue,
BALT : nodule
(II)The function and features of MALT
Local immunity
Secrete sIgA
Section III Lymphocytes homing and recirculation
I. Lymphocyte homing
The process by which particular subsets of
lymphocytes selectively enter some tissues
but not others is called lymphocyte homing
II. lymphocyte recirculation
The continuous movement of lymphocytes
between blood stream and peripheral
lymphoid tissues is called lymphocyte
1. Pathway of lymphocyte recirculation
2. Significance of lymphocyte recirculation
Lymphoid node-blood recirculation
Enter into paracortex of Lymphoid node
by high endothelial venules (HEV) in
efferent lymphatics
Thoracic duct
Tissue –lymphoid node-blood recirculation
Afferent lymphatics
Lymphoid node
Spleen-Blood recirculation
Enter into white pulp of spleen via
central artery
spleen venule
Significance of lymphocyte recirculation
Renew the lymphocytes in peripheral
lymphoid organs
Maximize the chances of specific encounter
with antigen and initiation of adaptive
Enable lymphocytes to lymphoid tissue
throughout body and facilitate immune
response to antigen
MALT, Central immune organs, Peripheral immune
organs, lymphocyte recirculation, Lymphocyte
2. Questions :
Significance of lymphocyte recirculation
The function of thymus, bone marrow, spleen , LN and